Self-Assembled Glucose and Thermo Dual-Responsive Micelles of an Amphiphilic Graft Copolymer

Amphiphilic copolymers P(PBA)-g-P(PEG) containing poly(phenylboronic acid) (PPBA) and poly(ethylene glycol) (PEG) side chains were synthesized by copolymerization of 4-vinylphenylboronic acid (PBA) and poly(ethylene glycol) methyl ether methacrylate. The surface tension results showed that the critical micelle concentration (CMC) of P(PBA)-g-P(PEG) was 0.09 g/L. TEM revealed that these copolymers self-assembled into regular sphere micelles above CMC. The photon correlation spectroscopy suggested that they had unique performance of thermo-induced self-assembly. Above critical micelle temperature, they self-assembled into monodisperse micelles with thermosensitivity. Hydrodynamic diameters of these micelles increased dramatically in the presence of glucose. The glucose-regulated drug release behavior was observed through UV-vis spectroscopy.     

Deformable thermoelectric sponge based on layer-by-layer self-assembled transition metal dichalcogenide nanosheets for powering electronic skin

In this study, we fabricated mechanically deformable thermoelectric sponges comprising transition metal dichalcogenides (TMDs) and polyethyleneimine (PEI) through a layer-by-layer (LBL) self-assembly technique for a thermoelectric power supply for electronic skin. Chemically exfoliated molybdenum sulfide (MoS₂) and niobium diselenide (NbSe₂) were prepared as p- and n-type room-temperature thermoelectric materials, respectively, and deposited on a melamine sponge via electrostatic bonding with PEI to obtain stable mechanical stretchability and low thermal conductivity. Five bilayers of LBL self-assembled thermoelectric sponges exhibited an enhanced thermoelectric performance and figure of merit, which resulted from the improvement in the Seebeck coefficient compared with that of pristine chemically exfoliated TMDs owing to the energy filtering effect and the extremely low thermal conductivity owing to the phonon scattering effect at several created interfaces and the porous structure of the sponge. Additionally, the thermoelectric sponges showed mechanical stability during operation under stretching and compression and mechanical durability over 10,000 cycles under 30% tensile strain. Finally, based on the proposed thermoelectric sponge, a power patch that can be installed on the back of a hand to produce electrical energy in real time was successfully demonstrated.     

Construction of covalently attached enzyme multilayer films based on the photoreaction of diazo-resins and glucose oxidase

A novel and facile approach to construct multilayered glucose oxidase (GOx) films on the surface of quartz or CaF₂ slides as well as gold electrodes for use as biosensing interfaces is described. Diazo-resins (DAR) as polycation and glucose oxidase as polyanion were alternately deposited into a multilayer structure using layer-by-layer self-assembly technique based on electrostatic interaction as driving force. Upon near UV irradiation, the adjacent interfaces of the multilayer reacted to form a crosslinking structure which greatly improved the stability of the enzyme films. These changes was monitored and confirmed by UV-vis and IR spectroscopy. Ellipsometric measurements reveal that the enzymes formed sub-molecule layers, and the thickness of the film shows a linear relationship with the number of assembled layers, demonstrating a spatially well-ordered manner in multilayer structure. The covalently attached enzyme multilayer film has a highly permeable structure, and can be used as biosensing interface. Electrochemical and analytical behavior of the enzyme electrodes was studied by cyclic voltammetry (CV) in the presence or absence of glucose. The sensitivity of the enzyme-modified electrodes was estimated through the analysis of voltammetric signals, which can be fine turned to the desired level by adjusting the number of attached bilayers.     

CRITICAL SELF-ASSEMBLY CONCENTRATION OF AN IONIC-COMPLEMENTARY PEPTIDE EAK16-I

Understanding the process of self-assembly of peptides has been important in various biomedical engineering applications. This work focuses on the effect of peptide concentration on the molecular self-assembly of an ionic-complementary peptide, EAK16-I (AEAKAEAKAEAKAEAK), in aqueous solution. The surface tension and self-assembled nanostructures were determined for a wide range of peptide concentrations using axisymmetric drop shape analysis-profile (ADSA-P) and atomic force microscopy (AFM), respectively. Surface tension measurements revealed a critical self-assembly concentration of 0.3 mg peptide/ml water, below which the surface tension decreased rapidly with increasing peptide concentration, and above which the surface tension remained at a constant, plateau value. There were two structural transitions observed with increasing peptide concentration: the first was from globular nanostructures to fibrils, and the second from the fibrils to relatively thick fibers. The second structural transition occurred at the critical self-assembly concentration as determined by the surface tension measurements. The nanostructural behavior of EAK16-I was compared with that of EAK16-II, which has the same amino acid composition but a different charge distribution. Salt effects were also examined by adding NaCl to the peptide solution. The salt addition facilitated the formation of peptide fibrils at low peptide concentrations but increased the critical self-assembly concentration, which occurred at 0.8 mg peptide/ml water in the presence of 20 mM NaCl. The structural transitions involved in the self-assembly of EAK16-I resemble those from protofibrils to fibrils observed with numerous naturally occurring peptides. An understanding of this structural transition may have relevance in the analysis and treatment of peptide/protein conformational diseases and have application in the production of self-assembled protein nanostructures.     

Catalysis of Transesterification Reactions by a Self-Assembled Nanosystem

Histidine-containing peptides self-assemble on the surface of monolayer protected gold nanoparticles to form a catalytic system for transesterification reactions. Self-assembly is a prerequisite for catalysis, since the isolated peptides do not display catalytic activity by themselves. A series of catalytic peptides and substrates are studied in order to understand the structural parameters that are of relevance to the catalytic efficiency of the system. It is shown that the distance between the His-residue and the anionic tail does not affect the catalytic activity. On the other hand, the catalytic His-residue is sensitive to the chemical nature of the flanking amino acid residues. In particular, the presence of polar Ser-residues causes a significant increase in activity. Finally, kinetic studies of a series of substrates reveal that substrates with a hydrophobic component are very suitable for this catalytic system.     

自组装技术及其在生物传感器中的应用研究

构造高度有序性和重复性的生物分子薄膜是提高生物传感器检测性能的关键,自组装膜以其原位自发形成、热力学稳定、制作方便简单、对基底材料形状要求低、可人为地通过合成来设计分子结构和进行分子剪裁等特点,应用于构筑电化学酶传感器,引起了广泛的关注。分析了自组装膜形成的原理,介绍了自组装技术在电极表面固定酶的方法,综述了自组装技术在生物传感器中的应用,展望了自组装技术应用的发展趋势。     

微米管制备与应用进展

纳米管是当今研究的热点，但微米管由于性质独特及应用广泛，仍然吸引了科学家极大的注意力。近年来人们通过各种方法制备了不同材料的微米管，对各种方法进行总结并探索一些新方法具有重要的意义，文中介绍了各种不同的微米管制备方法，并重点介绍了一下静电纺丝纤维模板法。     

Temperature-Dependent Phase Behaviors in Cylinder-Forming Block Copolymers

We demonstrate that the temperature-dependent phase behaviors of parallel and perpendicular cylinder-forming block copolymers are governed by domain-domain segregation forces inherently present in block copolymer material itself. With increasing temperature, a parallel cylinder-forming block copolymer experienced a parallel cylinder straightening process before the order-disorder transition (ODT) and did not show long-range composition fluctuations near the ODT temperature due to the weak segregation forces between the block domains. A perpendicular cylinder-forming block copolymer with a strong segregation force between the block domains displayed cylinder orientation transition from perpendicular to parallel below the ODT temperature. On the other hand, a perpendicular cylinder-forming block copolymer material with an exceptionally strong segregation force between the block domains maintained its initial perpendicular cylinder orientation up to near the ODT temperature. In both cases of perpendicular cylinder-forming block copolymers, submicrometer-scale long-range composition fluctuations were observed well above the ODT temperature due to their intrinsically strong segregation forces between the block domains.     

聚电解质的层层自组装模型及参数探讨

利用静电自组装技术在载波片基底上制备了壳聚糖/磺化木质素多层薄膜,并运用紫外―可见(UV-Vis)光谱等方法对其组装过程进行了表征。结果表明:壳聚糖/磺化木质素层层自组装是一个指数增长过程,其指数增长的数学模型可以描述为:Y=a×en/b+c,其中Y代表膜增长过程的吸光度、频率、质量、厚度等物理性能,n代表层数;a、b和c为常数。由于许多文献报道的自组装例也都可以用此指数增长模型进行描述,为此结合实验和文献数据对影响参数a、b和c的因素进行了探讨。     

微型器件的自装配技术

自组装技术起源于生物化学领域。20世纪90年代以来,这种新型的装配技术得到了关注并且经历了较快的发展,同时在微机电系统(MEMS)等研究领域显示了潜在的应用前景。本文阐述了自组装技术的发展,介绍了多种自组装方法,包括利用毛细力、重力以及亲水(疏水)力作为驱动的多种自组装过程,着重总结了自组装技术在MEMS领域的应用。